The butt welds installed on-site between the inner and outer rings of the tubular seat and the trapezoidal column of the bulb tubular unit are relatively thick and difficult to weld, and are subject to complex stresses such as shear stress, compressive stress, and vibration for a long time. In order to ensure the long-term safe operation of the power station, it is necessary to ensure that the quality of its welds complies with national and industry quality inspection standards. The use of time-of-flight diffraction ultrasonic testing (TOFD) can better detect welding defects and control weld quality. Through the research on TOFD inspection of pipe seat welds in Shaping II Hydropower Station, it has certain reference significance for the application of TOFD in the pipe seat weld inspection of large bulb tubular units.
